OK. time for a heads up. I'll start by quoting myself from almost a year ago;
So, things are developing as we expected
Those of you that are following the 11.10 beta know that Austin now has implemented DOWNWASH. Downwash is simply put air that is deflected downwards behind the wing and is one of the factors that produce lift. So behind the wing, the air flows at a downwards angle. HOWEVER, the downwash area is not just limited to the area just behind and above the wing, and I bet most of you do not know the magnitude and forces that are in play. Have a look at this photo (Below) I took a while back. You can see (on the very dirty A321) how the air moves around the wing, puts things in perspective. Upwash (in front) and downwash (behind).
So if you thought the air just rushes by your passenger window horizontally, you were wrong. As you can see, the direction of the air even far above and away from the wing is not horizontal. This downwash area also extends all the way back to the tail and (can) hit the horizontal stabilizer.
And this is where things get complicated. The downwash hitting the tail will cause an UP pitching moment. How much depends on the aircraft geometry. An aircraft with a high tail like an MD80 will hardly notice this, while a 737 will notice some even though the tail is 2-3 meters above the wing. So this affects normal flight.
ALSO, when an aircraft is landing, it enters what we call ground effect (GE). Many believe GE is one effect, but there are atleast 3 that we need to take into account. One of them is affected by downwash and change in pitching moment. When an aircraft approaches ground (less than 1 span) altitude, the downwash angle will get more shallow. This causes less downforce on the tail and you will get a nose DOWN tendency which will affect your landing. Also, it will affect your takeoff where the opposite happens. This is very complex stuff to put it mildly.
So what is going on right now? We are working with Austin providing documentation and tests to get the magnitude of these effects right. It also means that we will need to recalibrate the 737 to get it back to where it was.
The good news is that Austin now has implemented the designers need to save the aircraft for the new effects to take effect. In other words the 737 will perform as expected until we release an update with the recalibration. So nothing for you guy's to worry about. We do NOT recommend you open the aircraft and save it yourself. Most likely you will be out of trim in cruise and overpitch on takeoff etc.
M